Public interest in sports of all types has increased dramatically in recent years. Along with the increased interest, compensation to athletes at the professional level has attained heights almost unheard of a decade ago. As a result, competition among athletes for positions on high paying professional teams has brought about levels of performance, strength and endurance that seem to increase year after year. Because of the high level of athletic ability and skill at almost all levels of competition, participants must be in top condition in order to perform at the required levels. As a result, athletes at all levels of amateur and professional sports are participating in conditioning and injury prevention programs using a variety of equipment. Moreover, injuries in sports have increased, and rehabilitation programs have been designed to quickly return the injured athlete to his or her previous level of performance. Especially in contact sports, such as football, injury prevention and rehabilitation programs are now a year-round part of the athlete's routine.
There are available commercially numerous types of equipment to test and exercise every major body joint and muscle group. Such equipment is extremely effective and reasonably safe if properly used. However, such exercises designed to strengthen the muscles supporting the body joints sometimes create undesirable shear forces on the joint being conditioned or rehabilitated with the result that the program is not as effective as it might otherwise be. In some instances, these shearing forces that are exerted on a joint during exercise programs can be detrimental. This is primarily due to the manner in which the exercise equipment is designed. Generally, such equipment requires the person using it to exact force at a particular point on a limb which force is resisted by the equipment. Very often, however, the point of application of the force is at a point distant from a body joint, and during the exercise the contracting muscles apply a shearing effect to the joint.
There is therefore a need for an improved device which can minimize these shearing forces without interfering with or detracting from the desired conditioning or rehabilitating effect on the muscles.